A novel canola variety designated NS6703 and seed, plants and plant parts thereof. Methods for producing a canola plant that comprise crossing canola variety NS6703 with another canola plant. Methods for producing a canola plant containing in its genetic material one or more traits introgressed into NS6703 through backcross conversion and/or transformation, and to the canola seed, plant and plant part produced thereby. Hybrid canola seed, plant or plant part produced by crossing the canola variety NS6703 or a locus conversion of NS6703 with another canola variety.